Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Jim Cathey wrote: need to put a light on the GPs and see how many seconds they're staying on when cold. We're getting mid 30'sF in the morning so I should get a lengthy glow. Around freezing you should be seeing something like 30 seconds of glow. If you don't, just wait that long anyway before starting. It ought to start a lot better. (You don't need a functioning light to get a good start, if you know how long you're supposed to wait.) Until temps get well below freezing, between 5-10 seconds is as long as the dash lamp should remain illuminated (if the relay is properly working). By zero deg.(F) that might extend out to 15-20 sec (although the later plugs optimized for afterglow heat MUCH faster and take only 10-15 sec to reach 1180 deg C vs 30 seconds for the older style plugs). It is usually desirable to allow the plugs to heat for an additional 10-15 sec AFTER the dash light extinguishes before once temps drop below freezing. The time constant that controls the duration of the dash lamp and time until power is turned off consists of a temperature sensitive resistor and a capacitor. When stored without being periodically energized, the capacitors deteriorate and after as little as a year they may fail and the temperature defined delay drops to almost nothing. Sometimes they can be revived by cycling them many times - and sometimes that doesn't work. Marshall -- Marshall Booth Ph.D. Ass't Prof. (ret.) Univ of Pittsburgh School of Medicine [EMAIL PROTECTED]
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Thanks Jim,
Tomorrow I'll try to talk the MB dealer into replacing the relay. And the
real fun begins. ;-)
Larry T (67 MGB, 74 911, 78 240D, 91 300D)
www.youroil.net for Oil Analysis and Weber Parts
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- Original Message -
From: Jim Cathey [EMAIL PROTECTED]
To: Mercedes Discussion List mercedes@okiebenz.com
Sent: Sunday, November 26, 2006 6:33 PM
Subject: Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
gets to after x seconds. it maxs out at 20 seconds and 1750F and
while it
will maintain that temp if the GP stays on ot doesn't get any hotter.
It
just stays hot longer.
The extra heat goes into the engine. It's not wasted. Sounds
like your GP's are working fine, only the light timer is wonky.
-- Jim
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Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Jim Cathey wrote: need to put a light on the GPs and see how many seconds they're staying on when cold. We're getting mid 30'sF in the morning so I should get a lengthy glow. Around freezing you should be seeing something like 30 seconds of glow. If you don't, just wait that long anyway before starting. It ought to start a lot better. (You don't need a functioning light to get a good start, if you know how long you're supposed to wait.) Later glow plugs designed for afterstart glow function reach maximum temp (1180 deg C) after only 10-15 sec while the plugs used thru most of the '80s took 30 sec to get that hot and series plugs took a minute or so to get that hot. Marshall -- Marshall Booth Ph.D. Ass't Prof. (ret.) Univ of Pittsburgh School of Medicine [EMAIL PROTECTED]
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
rumor has it that LarryT wrote: BTW, I searched for a DMM that reads dc current to 30a or so and no one had them. I'll order one though. DMM can be hard to read the slope, or change over time. The current draw starts high, then drops back a bit as the plug warms up. My favorite way to test them is with an old add-a-gauge-under-the-dash-style ammeter. I had a +- 40A in my parts box. On a OM616 or OM617 with parallel plugs, I unplug the glow plugs from the relay. This seperates the plugs - they now each have there own wire. I then connect the ammeter between batter positive and each of the glowplug contacts in the connector. It's quick and easy to see if they all act the same. I don't know how this method will adapt to a newer engine, but the meter should work the same. I know Summit Racing sells an ammeter by itself. I believe AutoZone does too. --Philip
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
DMM can be hard to read the slope, or change over time. A fast-reading DMM, especially with the analog bar graph (like the Fluke 8x series) works fairly well for that. Cheap DMM's might convert slower, they might be harder to use. -- Jim
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Jim Cathey wrote: A fast-reading DMM, especially with the analog bar graph (like the Fluke 8x series) works fairly well for that. Cheap DMM's might convert slower, they might be harder to use. Don't trust the accuracy of cheap DMMs, either. Mine reads about 10% low on the voltage scales, these days. I need to change the battery and see if that helps.
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
I saw some Fluke's at Sears - for around ~$100. and some Simpson DMMs for
a similiar price. I'll probably get one in that price range which I hope
indicates a decent gauge. It's so frustrating to go into a store and find
they're sold out of the thing I want. It just boggles my mind that a store
would be sold out of a product - some sell out often and to me the easiest
thing is to keep enough stuff on the shelf so customers don't walk out empty
handed.
SOrry 'bout the rant.
Anyway - I'll get a DMM that will read dc current as well as the more
common readings -
Thanks again for everyone's help on troubleshooting my GP system- I'm
convinced something inside the relay is flakey and hopefully the dealer
won't give me a hardtime exchange it without a fight.
Larry T (67 MGB, 74 911, 78 240D, 91 300D)
www.youroil.net for Oil Analysis and Weber Parts
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- Original Message -
From: Jim Cathey [EMAIL PROTECTED]
To: Mercedes Discussion List mercedes@okiebenz.com
Sent: Sunday, November 26, 2006 10:00 PM
Subject: Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
DMM can be hard to read the slope, or change over time.
A fast-reading DMM, especially with the analog bar graph
(like the Fluke 8x series) works fairly well for that.
Cheap DMM's might convert slower, they might be harder to use.
-- Jim
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Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Thanks Phillip! What a great solution. Jim C suggested a solution using
old GP parts but I didnt have them - this is something I can pick up for
small $'s and I understand exactly how to use it from your description.
BTW, my GP system will work easily with your suggestion - I can unplug the
wiring harness that goes to the individual GPs from the relay - it'll be
easy to put the ammeter between the wire to each GP and the battery + side.
Thanks again!
Larry T (67 MGB, 74 911, 78 240D, 91 300D)
www.youroil.net for Oil Analysis and Weber Parts
Test Results http://members.rennlist.com/oil
PORSCHE POSTERS! youroil.net
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.
- Original Message -
From: Fmiser [EMAIL PROTECTED]
To: Mercedes Discussion List mercedes@okiebenz.com
Sent: Sunday, November 26, 2006 9:51 PM
Subject: Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
rumor has it that LarryT wrote:
BTW, I searched for a DMM that reads dc
current to 30a or so and no one had them. I'll order one though.
DMM can be hard to read the slope, or change over time.
The current draw starts high, then drops back a bit as the plug warms
up.
My favorite way to test them is with an old
add-a-gauge-under-the-dash-style ammeter. I had a +- 40A in my parts
box.
On a OM616 or OM617 with parallel plugs, I unplug the glow plugs from
the relay. This seperates the plugs - they now each have there own
wire. I then connect the ammeter between batter positive and each of
the glowplug contacts in the connector. It's quick and easy to see if
they all act the same.
I don't know how this method will adapt to a newer engine, but the
meter should work the same. I know Summit Racing sells an ammeter by
itself. I believe AutoZone does too.
--Philip
___
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Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
BTW, my GP system will work easily with your suggestion - I can unplug the wiring harness that goes to the individual GPs from the relay - it'll be easy to put the ammeter between the wire to each GP and the battery + side. Even easier is to use the screw that mounts the 80A fuse. That's hot all the time, and is right next to the plug. -- Jim
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
For electronics I have a Fluke 189, for automotive stuff I keep a $3 harbor
freight multimeter in each car. I have rarely found any time I needed a more
expensive multimeter for car work.
A friend of mine has a $400 Snap On multimeter, which I refuse to use. It
has a little problem that when the battery is low it will read voltages
wrong. He replaced at least two alternators in a car due to the meter
reading the voltages low.
Fluke in my opinion is the best multimeters but you do not need that level
of performance for occasional use.
I also have a hall effect clamp on current meter, they are awesome and I use
mine a lot on just on cars but other items as well. For example checking a
water heater element over the weekend, it had power and with current meter I
just clamped on and verified that current was zero to know it was bad.
Otherwise I would had to cut power and measure resistance.
Trampas
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Jim Cathey
Sent: Monday, November 27, 2006 9:22 AM
To: Mercedes Discussion List
Subject: Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
I saw some Flukes at Sears - for around ~$100. and some Simpson DMM's
for
a similiar price. I'll probably get one in that price range which I
hope
indicates a decent gauge.
It was a few years ago, but my (then-new) Fluke was more like $300.
I know they've come down since then! The true-RMS ones are superior,
and more expensive, but that may not matter to you.
Anyway - I'll get a DMM that will read dc current as well as the more
common readings -
I've never seen a commonly-available DMM that will measure more than
10A directly, including my Flukes. Some kind of adapter is needed to
go beyond that. The cool thing, of course, is the clamp-on hall-effect
current probe.
-- Jim
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Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Jim wrote:I don't know what you mean about the 'feel' of 4 GP's should have said it feels like its running on 4 cylinders out of 5. Also -when I tested the GPs with my Bat Chgr I should have mentioned it has a gauge on it - it was pegged at 15 amps on each trial. Don't know how accurate the gauge is - the charger is 20 years old. So I was able to test GP dc current draw after all - sort of. But I guess with it pegged it's not telling me much. BTW, I searched for a DMM that reads dc current to 30a or so and no one had them. I'll order one though. Marshalls suggestion about the TSB comment to cycle the relay to try and revive it is worth a try unless MB agrees to replace it - it's only 4-5 weeks old after all. I'll try to keep the battery from dieing. Also, I need to put a light on the GPs and see how many seconds they're staying on when cold. We're getting mid 30'sF in the morning so I should get a lengthy glow. I have to go to the dealer anyway to get the correct intake man gasket - they gave me a 6 cyl one by mistake. BTW, the wiring harness is in great condition - the car has 115000 babied miles on it and everything I come across as I work my way thru maint. items looks like its been well cared for or original. Thanks for everyong help - Larry T (67 MGB, 74 911, 78 240D, 91 300D) www.youroil.net for Oil Analysis and Weber Parts Test Results http://members.rennlist.com/oil PORSCHE POSTERS! youroil.net Weber Carb Info http://members.rennlist.com/webercarbs Porsche Road Test http://members.rennlist.com/roadtest/ . - Original Message - From: Jim Cathey [EMAIL PROTECTED] To: Mercedes Discussion List mercedes@okiebenz.com Sent: Sunday, November 26, 2006 3:24 PM Subject: Re: [MBZ] GP Infant Mortality tested them by attaching each in turn to a Batt chgr and all glowed red hot at the tip within ~12 sec. from the chart in the book that's pretty good - of course, they're all only about 4 weeks old. That sounds good. A plug can still get hot yet draw out-of-spec current, possibly enough to PO the GP relay. But if all five acted exactly the same the chances of this are lessened. Ok, the relay was replaced 4 weeks ago also after it failed to light up the GPs one night when my wife wanted to come home. A new replay gets the GPs to light but the light goes out within 1 sec (about 1/5 sec) and it feels like only 4 GPs are preglowing. The light is hooked to a temperature-sensitive timer. The GP's are hooked to a _different_ timer. They have nothing to do with each other, except that both are started with the key. If all five GP's do not heat up, and stay heating for something like 90+ seconds before automatically cutting off, then the GP relay is defective. With good GP's, if the light does not obey the ambient temperature/time curve that's in the (some, anyway) manuals, then it is defective. I don't know what you mean about the 'feel' of 4 GP's. What do you think? Should I just button things up? If we have definitively diagnosed the relay, yes. Unless you want to dive into the relay's guts to try to repair it. Bad for warrantee issues, and you risk making things worse too. If you still have your old one, of course... There was a TSB about cycling a preglow relay that exhibited foreshortened intervals about 10-12 times in a row (turn on the glow plugs and allow them to remain on until the relay cut off - and repeat 10-12 times - will likley run the battery down, but MAY revive the relay and timing MAY return to normal). This TSB (early/mid '80s as I recall) referred to new and used preglow relays that exhibited short timing intervals after being stored and not used for months or years. This is SOP for reforming an electrolytic capacitor, since the days of vacuum tubes. It doesn't always work, of course, but is worth a try. To save your battery just unplug the GP harness. The timers should still do their cycling, which should do any possible reformation during that time. To _really_ reform a cap, you need to take it out of circuit. At that point, of course, you'd just replace it. -- Jim ___ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.409 / Virus Database: 268.14.16/552 - Release Date: 11/26/2006
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
need to put a light on the GPs and see how many seconds they're staying on when cold. We're getting mid 30'sF in the morning so I should get a lengthy glow. Around freezing you should be seeing something like 30 seconds of glow. If you don't, just wait that long anyway before starting. It ought to start a lot better. (You don't need a functioning light to get a good start, if you know how long you're supposed to wait.) -- Jim
Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
Jim wrote:should be seeing something like 30 seconds
of glow. If you don't, just wait that long anyway
That's what we've *been* doing since I replaced the GPs and relay - but I
want the preglow relay light to work properly. And it sounds like a new
relay will be needed to make that happen. I read the chart in the WSM
showing the various glow times needed and the curve showing the temp the GP
gets to after x seconds. it maxs out at 20 seconds and 1750F and while it
will maintain that temp if the GP stays on ot doesn't get any hotter. It
just stays hot longer.
It starts instantly - we count to 15 when it's cold and it always starts on
the 1st 1/2 revolution.
Even when it was around 15F it starts after 15 seconds of glowtime. Always
starts instantly.
Larry T (67 MGB, 74 911, 78 240D, 91 300D)
www.youroil.net for Oil Analysis and Weber Parts
Test Results http://members.rennlist.com/oil
PORSCHE POSTERS! youroil.net
Weber Carb Info http://members.rennlist.com/webercarbs
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.
- Original Message -
From: Jim Cathey [EMAIL PROTECTED]
To: Mercedes Discussion List mercedes@okiebenz.com
Sent: Sunday, November 26, 2006 5:17 PM
Subject: Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
need to put a light on the GPs and see how many seconds they're
staying on
when cold. We're getting mid 30'sF in the morning so I should get a
lengthy
glow.
Around freezing you should be seeing something like 30 seconds
of glow. If you don't, just wait that long anyway before starting.
It ought to start a lot better. (You don't need a functioning light
to get a good start, if you know how long you're supposed to wait.)
-- Jim
___
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Re: [MBZ] GP Infant Mortality ('91 300D 2.5T W124)
gets to after x seconds. it maxs out at 20 seconds and 1750F and while it will maintain that temp if the GP stays on ot doesn't get any hotter. It just stays hot longer. The extra heat goes into the engine. It's not wasted. Sounds like your GP's are working fine, only the light timer is wonky. -- Jim
